4 ms·

I hope they will build CANDU 9 reactors. CANDU is easily one of the best commercially available reactor designs available, because it can be refueled while it's

I hope they will build CANDU 9 reactors. CANDU is easily one of the best commercially available reactor designs available, because it can be refueled while it's running, the uranium doesn't need to be enriched, and it could technically breed and burn Thorium. Plus, it is indigenous and could create a ton of Canadian jobs.

credit_guy 3y ago
I like CANDU reactors, but I like pressurized water reactors (PWR) reactors more. PWR reactors are the majority of the active commercial reactors in the world. The advantages of the CANDU reactors over PWR reactors can be seen as disadvantages, actually. 1. Ability to refuel without stopping the reactor. That's a very convenient feature if you intend to make nuclear bombs. Seen differently, if you want to reduce proliferation risks, PWRs are better. 2. Usage of unenriched uranium. It's not like you just put in the reactor uranium straight out of a mine. You need to process it, if only to clad it in zirconium. You buy the nuclear fuel from approved sources, like Westinghouse. The enriched fuel will be more expensive, but you get more energy out of it. Put it differently, for the same amount of energy PWRs produce less spent fuel than CANDU reactors. 3. Thorium. In principle you can put thorium in a Candu reactor and get uranium-233 which you can then burn to get energy. In practice, this idea was talked about for many decades, but for some reason nobody does it. Including India: they have lots of thorium, lots of Candu reactors, but they don't burn thorium in their Candu reactors. Why? Very likely because of the contamination with uranium-232 which gives strong gamma radiation. But let's say that you do actually find a way to use thorium to breed U-233. That increases the proliferation risk tremendously. Here's an interesting quote from [1] The half-lives of the protactinium isotopes work in the favor of potential proliferators. Because protactinium 232 decays faster than protactinium 233, the isotopic purity of protactinium 233 increases as time passes. If it is separated from its uranium decay products a second time, this protactinium will decay to equally pure uranium 233 over the next few months. With careful attention to the relevant radiochemistry, separation of protactinium from the uranium in spent thorium fuel has the potential to generate uranium 233 with very low concentrations of uranium 232—a product suitable for making nuclear weapons. Your last point about Candu creating lots of jobs: I think a PWR reactor would create exactly the same number of jobs. And now, the biggest reason in favor of a PWR reactor: all reactors have various feedback effects. Some of these effects are negative, some positive. You want to have more negative feedback effects (i.e. passive safety features) and few positive feedback effects (i.e. possible instability scenarios). PWR reactors are the most stable reactors among the current generation reactors. Candu reactors have many of the same negative feedback effects as the PWR reactors, but there's an exception: positive void coefficient. The Canadian nuclear regulator is aware, obviously [2], and thinks this is not a biggie. But when you can choose between two designs, one with more passive safety features than the other, why not choose the first? [1] https://thebulletin.org/2018/08/thorium-power-has-a-protactinium-problem/ https://thebulletin.org/2018/08/thorium-power-has-a-protacti... [2] https://nuclearsafety.gc.ca/eng/resources/videos/player/index.cfm?videoid=void-coefficient-of-reactivity https://nuclearsafety.gc.ca/eng/resources/videos/player/inde...
- evilos 3y ago
  Proliferation concerns for reactors are silly IMO. Any nation state with access to U and graphite can simply construct a pile reactor to make Pu. Much easier to conceal and operate compared to trying to mask reactor operations at a civilian plant. Plus with a CANDU, the fuel patterns for making energy are incompatible with the ones for making Pu so it would be very obvious. The cat has been out of the bag for a while. Most major nation states could come up with a crude nuclear weapon in a few years or less if they wanted to. The existence of civilian energy facilities is irrelevant to the weapons question. We might as well reap the benefits of fission if we must live with its drawbacks.
  - credit_guy 3y ago
    > Any nation state with access to U and graphite can simply construct a pile reactor to make Pu. Much easier to conceal and operate compared to trying to mask reactor operations at a civilian plant. The pile reactor that the US built during WW2 at the Hanford Site employed 45000 construction workers. Making plutonium is quite straightforward in theory, but practice tends to disagree with theory. Two nations that I know of decided that uranium bombs make more sense for them, South Africa and Iran. South Africa went on to build six such bombs.
    - evilos 3y ago
      Looks like 40k workers was the peak during construction. And to be fair, it was also the 1940's, they were in a massive rush, and it was the literal first time it was done.

credit_guy 3y ago

I like CANDU reactors, but I like pressurized water reactors (PWR) reactors more. PWR reactors are the majority of the active commercial reactors in the world. The advantages of the CANDU reactors over PWR reactors can be seen as disadvantages, actually. 1. Ability to refuel without stopping the reactor. That's a very convenient feature if you intend to make nuclear bombs. Seen differently, if you want to reduce proliferation risks, PWRs are better. 2. Usage of unenriched uranium. It's not like you just put in the reactor uranium straight out of a mine. You need to process it, if only to clad it in zirconium. You buy the nuclear fuel from approved sources, like Westinghouse. The enriched fuel will be more expensive, but you get more energy out of it. Put it differently, for the same amount of energy PWRs produce less spent fuel than CANDU reactors. 3. Thorium. In principle you can put thorium in a Candu reactor and get uranium-233 which you can then burn to get energy. In practice, this idea was talked about for many decades, but for some reason nobody does it. Including India: they have lots of thorium, lots of Candu reactors, but they don't burn thorium in their Candu reactors. Why? Very likely because of the contamination with uranium-232 which gives strong gamma radiation. But let's say that you do actually find a way to use thorium to breed U-233. That increases the proliferation risk tremendously. Here's an interesting quote from [1] The half-lives of the protactinium isotopes work in the favor of potential proliferators. Because protactinium 232 decays faster than protactinium 233, the isotopic purity of protactinium 233 increases as time passes. If it is separated from its uranium decay products a second time, this protactinium will decay to equally pure uranium 233 over the next few months. With careful attention to the relevant radiochemistry, separation of protactinium from the uranium in spent thorium fuel has the potential to generate uranium 233 with very low concentrations of uranium 232—a product suitable for making nuclear weapons. Your last point about Candu creating lots of jobs: I think a PWR reactor would create exactly the same number of jobs. And now, the biggest reason in favor of a PWR reactor: all reactors have various feedback effects. Some of these effects are negative, some positive. You want to have more negative feedback effects (i.e. passive safety features) and few positive feedback effects (i.e. possible instability scenarios). PWR reactors are the most stable reactors among the current generation reactors. Candu reactors have many of the same negative feedback effects as the PWR reactors, but there's an exception: positive void coefficient. The Canadian nuclear regulator is aware, obviously [2], and thinks this is not a biggie. But when you can choose between two designs, one with more passive safety features than the other, why not choose the first? [1] https://thebulletin.org/2018/08/thorium-power-has-a-protactinium-problem/ https://thebulletin.org/2018/08/thorium-power-has-a-protacti... [2] https://nuclearsafety.gc.ca/eng/resources/videos/player/index.cfm?videoid=void-coefficient-of-reactivity https://nuclearsafety.gc.ca/eng/resources/videos/player/inde...

evilos 3y ago
Proliferation concerns for reactors are silly IMO. Any nation state with access to U and graphite can simply construct a pile reactor to make Pu. Much easier to conceal and operate compared to trying to mask reactor operations at a civilian plant. Plus with a CANDU, the fuel patterns for making energy are incompatible with the ones for making Pu so it would be very obvious. The cat has been out of the bag for a while. Most major nation states could come up with a crude nuclear weapon in a few years or less if they wanted to. The existence of civilian energy facilities is irrelevant to the weapons question. We might as well reap the benefits of fission if we must live with its drawbacks.
- credit_guy 3y ago
  > Any nation state with access to U and graphite can simply construct a pile reactor to make Pu. Much easier to conceal and operate compared to trying to mask reactor operations at a civilian plant. The pile reactor that the US built during WW2 at the Hanford Site employed 45000 construction workers. Making plutonium is quite straightforward in theory, but practice tends to disagree with theory. Two nations that I know of decided that uranium bombs make more sense for them, South Africa and Iran. South Africa went on to build six such bombs.
  - evilos 3y ago
    Looks like 40k workers was the peak during construction. And to be fair, it was also the 1940's, they were in a massive rush, and it was the literal first time it was done.